Intravascular stents having a constricted diameter for delivery through a blood vessel and an expanded diameter for applying a radially outwardly extending force for supporting the blood vessel are known in the art. Both self-expandable stents and balloon expandable stents are well known.
In conventional stent mounting and securing procedures, the stent is usually first slid over the distal end of a balloon catheter so that the expandable balloon is disposed within the longitudinal bore of the stent. The stent is then crimped to mount or secure the stent and maintain its position with respect to the expandable balloon as the balloon catheter is advanced to the target area.
Typical catheters for interventional angioplasty are based on a catheter that rides on a guide wire. The guide wire has some characteristics of flexibility and pushibility that may vary along its length. The catheter (balloon catheter) also has some characteristics of flexibility and stiffness that may vary along its length. The variations of flexibility and pushibility do not match each other as the catheter tracks along different sections of the wire. Also, the profile of the catheter has to permit the free ride of an internal lumen in the catheter over the wire, resulting in a bigger profile and less flexible catheter shaft. The tip of the balloon catheter may latch on plaque when pushed to the vessel wall by the guide wire and thus prevent insertion through constricted areas and through another stent.
An arrangement which does not use a guide wire that slides through the balloon of the balloon angioplasty catheter is disclosed in European Patent Application EP 1 101 455 A2. In that arrangement, a stent delivery system is provided for percutaneous insertion into a vessel of the human body in order to place a balloon expandable stent at the site of an obstruction in the vessel. The stent delivery system includes a balloon angioplasty catheter having a distal section with an inflatable balloon located at the distal section of the balloon angioplasty catheter. A balloon expandable stent is co-axially mounted on the inflatable balloon. A flexible guide wire is fixedly attached to and extends distally from the distal section of the balloon angioplasty catheter.
In today's arena where direct stenting has become very popular and no other catheter is threaded on the guide wire before, or after the stent delivery system, such a stent delivery system that is combined with a wire tip at its forward end becomes quite reasonable. It can solve the problems of optimal flexibility transition, optimal profile and elimination of “steps” between the catheter tip and the wire. Furthermore, it can make for a faster and less traumatic procedure with one insertion instead of two (wire and then catheter). Thus, a catheter with a wire tip at the length of a single operator catheter does not require a second hand for holding the wire during the insertion of the catheter, and thus forms a single operator stent system.
However, one of the disadvantages of an arrangement such as that shown in EP 1 101 455 A2 is that today there are at least three different classes of guide wires used. These differ in their overall flexibility and the arrangement of different sections with different flexibility (e.g. floppy wire, soft wire, hard wire, super-hard wire etc.). The selection of wire is often dictated by the conditions on the way to a lesion to be treated and not by the lesion itself.
Once the leading wire is combined with the balloon, the freedom to select different types of wire is lost. One solution would be to multiply the line of crimped stent systems to have parallel systems with different wire tips. This is obviously a complex and costly solution. Thus, there is a need for a single operator stent system, which avoids this loss of freedom in an effective and cost efficient manner.